Herpes simplex virus (HSV) produces highly communicable, recurring infections afflicting some 20 million Americans, with approximately 400,000 new cases annually. There is as yet to known cure. The Microbiology and Infectious Diseases Program of the National Institute of Allergy and Infectious Diseases has identified the development of antiviral drugs directed at herpes virus as a specific research area deserving support. Polysaccharides of red algae of the family Dumontiaceae have been shown to exhibit specific activity against HSV in in vitro cell cultures. Preliminary evidence of in vivo activity has also been presented. The objective of the proposed research is to further investigate the chemical structure and mechanism of activity of these compounds with a view to their eventual therapeutic application. In the proposed Phase I effort, red algae would be collected and their ecological distribution and abundance noted. Specimens of selected algae will be held on farm structures in the sea to determine amenability for cultivation. Members of the Dumontiaceae and other families that have not been tested previously will be sought for testing. Emphasis will be placed on obtaining representatives of major taxonomic groups that have not been tested. Anti-HSV activity will be assessed by challenging mammalian cell cultures with HSV types 1 and 2 with and without algal extracts. Red algae collected in this study would ultimately be supplied to a pharmaceutical research laboratory for further study and in vivo testing. This research should result in 1) valuable information regarding the distribution and abundance of anti-HSV red algae, 2) indications of the amenability of these algae to cultivation, and 3) the demonstration that other red algae not tested previously also exhibit anti-HSV activity. The commercial applicability of agents that show anti-HSV activity is self-evident.